<?php
if (isset($_POST['txn_id'])) {
    echo '<pre>';
    print_r($_POST);
    echo '</pre>';
}
// paypal sandbox
// dungtv_1321430960_biz@ic-t.info/321430924

/* Array
  (
  [mc_gross] => 3.00
  [protection_eligibility] => Ineligible
  [address_status] => confirmed
  [payer_id] => LVMM7AGWTJDSC
  [tax] => 0.00
  [address_street] => 1 Main St
  [payment_date] => 08:11:05 Nov 20, 2011 PST
  [payment_status] => Pending
  [charset] => windows-1252
  [address_zip] => 95131
  [first_name] => Tran
  [address_country_code] => US
  [address_name] => Tran Dung's Test Store
  [notify_version] => 3.4
  [custom] => custom fields
  [payer_status] => verified
  [address_country] => United States
  [address_city] => San Jose
  [quantity] => 1
  [payer_email] => dungtv_1321430960_biz@ic-t.info
  [verify_sign] => AFXUG7PZPkETAVPyj3qGpxNDGAtKA5Q2lgKvyb9.3RUSNf0fbyRYYyhu
  [txn_id] => 30783352KU427533F
  [payment_type] => instant
  [payer_business_name] => Tran Dung's Test Store
  [last_name] => Dung
  [address_state] => CA
  [receiver_email] => dungtv@ic-t.info
  [pending_reason] => unilateral
  [txn_type] => web_accept
  [item_name] => Test paypal ipn
  [mc_currency] => USD
  [item_number] => 1
  [residence_country] => US
  [test_ipn] => 1
  [transaction_subject] => custom fields
  [handling_amount] => 0.00
  [payment_gross] => 3.00
  [shipping] => 0.00
  [merchant_return_link] => click here
  [form_charset] => UTF-8
  ) */
?>

<form name="_xclick" action="https://www.sandbox.paypal.com/cgi-bin/webscr" method="post">
    <input type="hidden" name="cmd" value="_xclick" />
    <input type="hidden" name="business" value="dungtv@ic-t.info" />
    <input type="hidden" name="currency_code" value="USD" />
    <input type="hidden" name="item_name" value="Test paypal ipn" />
    <input type="hidden" name="item_number" value="1" />
    <input type="hidden" name="amount" value="3" />
    <input type="hidden" name="custom" value="" />
    <input type="hidden" name="return" value="http://local.studybuddy.com.sg/paypaltest.php" />
    <input type="hidden" name="notify_url" value="http://local.studybuddy.com.sg/ipn.php" />
    <input type="image" src="http://www.paypal.com/en_US/i/btn/btn_buynow_LG.gif" border="0" name="submit" alt="Make payments with PayPal - it's fast, free and secure!" />
</form>
